In recent electronic component mounting apparatus, an electronic component adsorbed by an adsorption nozzle is imaged by a camera during a period between adsorption of the electronic component by the adsorption nozzle and mounting of the electronic component on a circuit board. Based on a pickup image, appearance information (size or the like, for example) and adsorbed location information (a central position and inclination θ of the component and the like, for example) are detected so that an accuracy in a mounted position of the electronic component is ensured or so that mounting of defective components can be prevented. In this case, in order that a mounting efficiency may be improved, a plurality of electronic components adsorbed by a plurality of adsorption nozzles respectively are caused to come within a visual field of a camera at the same time and imaged so that appearance information and adsorbed location information are detected at a single time of imaging, as shown in FIGS. 1A and 1B.
Since cameras generally have parallax, the cameras have characteristics that an image of an electronic component becomes smaller (magnification of image is reduced) as the electronic component to be imaged is spaced farther away from the camera and as the image is shifted away from the center of the visual field of the camera. Accordingly, as shown in FIG. 1B, even when an electronic component to be imaged is actually rectangular in shape, the parallax of the camera deforms an image of the electronic component into a trapezoidal shape, or a height (thickness) of the electronic component changes a distance between the camera and the electronic component such that the size of an obtained image of the electronic component is changed. In particular, when a plurality of electronic components are imaged by a camera at the same time, a plurality of electronic components to be imaged have different heights or horizontal distances between the center of the visual field of the camera and the electronic components differ from each other. Accordingly, a degree of deformation in pickup image and a degree of scale-down in an image size differ in every electronic component, whereupon appearance information and adsorbed position information of each electronic component cannot accurately be detected.
In order to overcome the above-described problems due to the camera parallax, the following patent document 1 proposes an arrangement in which a telecentric lens for parallax correction is disposed in front of the camera and an electronic component is imaged so that a pickup image of the electronic component basically remains unchanged even when the position of the electronic component changes.
Patent document 1: JP-A-2001-217599